During some construction projects, such as building out the interior of a large building under construction, or renovating an older building, it is extremely useful to refer to Building Information Modeling (BIM) data. This data, when available, defines the building structure, including the interior, in three dimensions, and its use increases the productivity of construction workers by facilitating the location and placement of various building construction elements and fixtures. Typically, the BIM model of the building is maintained after the building construction is completed, and can be used over the life of the building for construction, expansion, and maintenance purposes. The BIM model defines building geometry, spatial relationships, and quantities and properties of building components.
During new construction or renovation, it is extremely useful to be able to locate quickly various construction points in three dimensions within the building interior. As the interior of a building is being finished, connectors, anchors and the like are attached to the floors, ceilings and other structures in the building, and cuts are made and holes drilled using power saws and drills. All of this must be accomplished at predetermined, precisely defined positions in the building interior. For example, nail guns, power saws, powder anchor tools, and the like are used to nail, cut, install fasteners, and perform other operations at predetermined points within the building with little error. Additionally, a large number of electrical, plumbing, and HVAC components must be properly sited and installed. The construction points for all of these building elements must be located quickly and with some precision with respect to the surrounding walls, ceilings and floors, as they are roughed in. Typically, a substantial amount of time and effort has been required to lay out the many construction points at such a construction site. Teams of workers have been needed to measure and mark predetermined locations. It will be appreciated that this process has been subject to errors, resulting from measurement mistakes and from accumulated errors. Further, the cost of this layout process and the time needed to perform the layout process have both been significant.
Layout of the construction points at a building interior construction site has been accomplished in more automated ways, such as for example by using a robotic total station device, positioned within the building. The total station is positioned at a fixed, known location and directs a beam of laser light to a desired location. The beam may illuminate a floor, ceiling or wall at a point or may be directed to, and reflected from a target, such as a retroreflective target. By measuring the time of travel of the beam from the total station to the surface or target and then back to the total station, the distance to the target is determined. The directional orientation of the beam to the target is also known. Since the dimensional coordinates of the total station are known, the dimensional coordinates of the target can easily be determined. One or more retroreflective elements may be positioned on a tool so that the position and orientation of the tool can be determined in relation to the building interior. Alternatively, the total station may simply direct a beam of visible laser light to illuminate a predetermined point on a wall, ceiling, floor or other building element where a construction operation is to be performed.
It will be appreciated, however, that a large number of construction points must typically be located within a building interior construction site. A difficulty may arise in locating the robotic total station within the interior area of the building under construction so that it has line-of-sight access to all of the construction points to be located. It is not uncommon that the user finds that a position selected for positioning the robotic total station results in some of the construction points being blocked by columns, walls, or other interior features of the building. Repeated repositioning of the robotic total station to avoid obstructions is an inconvenience, and reduces the efficiency gains that can be obtained through the use of the device in the layout process.